Blood Glucose and Exercise

There are a few ways that exercise lowers blood glucose:

  • Insulin sensitivity is increased, so your muscle cells are better able to use any available insulin to take up glucose during and after activity.
  • When your muscles contract during activity, your cells are able to take up glucose and use it for energy whether insulin is available or not.

This is how exercise can help lower blood glucose in the short term. And when you are active on a regular basis, it can also lower your A1C.

Understanding Your Blood Glucose and Exercise

The effect physical activity has on your blood glucose will vary depending on how long you are active and many other factors.  Physical activity can lower your blood glucose up to 24 hours or more after your workout by making your body more sensitive to insulin.

Become familiar with how your blood glucose responds to exercise. Checking your blood glucose level more often before and after exercise can help you see the benefits of activity. You also can use the results of your blood glucose checks to see how your body to reacts to different activities. Understanding these patterns can help you prevent your blood glucose from going too high or too low.

Hypoglycemia and Physical Activity

People taking insulin or insulin secretagogues (oral diabetes pills that cause your pancreas to make more insulin) are at risk for hypoglycemia if insulin dose or carbohydrate intake is not adjusted with exercise. Checking your blood sugar before doing any physical activity is important to prevent hypoglycemia (low blood sugar).  Talk to your diabetes care team (doctor, nurse, dietitian or pharmacist) to find out if you are at risk for hypoglycemia.

If you experience hypoglycemia during or after exercise, treat it immediately:

Follow the 15-15 rule:

1. Check your blood glucose.

2. If your reading is 100 mg/dL or lower, have 15-20 grams of carbohydrate to raise your blood glucose. This may be:

    4 glucose tablets (4 grams per tablet), or

    1 glucose gel tube (15 grams per gel tube), or

    4 ounces (1/2 cup) of juice or regular soda (not diet), or

    1 tablespoon of sugar or honey

3. Check your blood glucose again after 15 minutes. If it is still below 100 mg/dL, have another serving of 15 grams of carbohydrate.

4. Repeat these steps every 15 minutes until your blood glucose is at least 100 mg/dL.

If you want to continue your workout, you will usually need to take a break to treat your low blood glucose. Check to make sure your blood glucose has come back up above 100 mg/dl before starting to exercise again.

Keep in mind that low blood glucose can occur during or long after physical activity. It is more likely to occur if you:

  • Take insulin or an insulin secretagogue
  • Skip meals 
  • Exercise for a long time
  • Exercise strenuously

If hypoglycemia interferes with your exercise routine, talk to your healthcare provider about the best treatment plan for you. Your provider may suggest eating a small snack before you exercise or they may make an adjustment to your medication(s). For people engaging in long duration exercise, a combination of these two regimen changes may be necessary to prevent hypoglycemia during and after exercise.

  • Last Reviewed: September 4, 2013
  • Last Edited: September 25, 2017

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